Fuel injection system

ABSTRACT

A fuel-injection system for internal combustion engines has at least one fuel injector injecting fuel into a combustion chamber, which is delimited by a cylinder wall in which a piston is guided. A spark plug projects into the combustion chamber, and the fuel injector is located in the combustion chamber in the region of a gas-intake valve toward the cylinder wall. The fuel injector produces a plurality of fuel jets at least one of these fuel jets being tangentially oriented to the region of the spark plug.

FIELD OF THE INVENTION

[0001] The present invention is directed to a fuel injection system.

BACKGROUND INFORMATION

[0002] In mixture-compressing internal combustion engines havingexternal ignition and internal mixture formation, stratified chargeoperation requires a “mixture cloud” in the region of the spark plug,which must have a particular fuel-air ratio in the ignitable range.Especially in partial load operation and during idling, this has aconsiderable effect on fuel consumption since the entire combustionchamber volume is not filled with an enriched, ignitable mixture.

[0003] Basically, three methods are known for producing such a mixturecloud: the wall-directed, the air-directed and the jet-directedfuel-injection system.

[0004] In the wall-directed fuel-injection system, the fuel is carriedalong by an air vortex which lies up against the wall of the cylinderand in most cases is deflected at the specially designed piston. Forthis purpose, a fuel injector, which is positioned at the side of theintake valve toward the cylinder wall, injects the fuel into a vortexnear the wall surface of the cylinder and/or onto the piston surface.The vortex causes the fuel to be carried along to the spark plug in thecenter of the combustion chamber, a mixture being formed at the sametime.

[0005] A wall-directed fuel-injection system is known from EuropeanPublished Patent Application No. 0 519 275, for instance. A spark plugis positioned in a center section of an inner wall of a cylinder head,and a fuel-injection device is located at a circumferential section ofthe inner wall of the cylinder head. A piston has an indented sectionbeneath the spark plug, onto whose surface the fuel is injected at aslant, the fuel being deflected at the edge of the indented surface. Avortex carries along the fuel in the direction of the spark plug.

[0006] Disadvantageous in this related art is that theturbulence-producing measures, such as special designs of thecombustion-chamber geometry, especially the piston form designs, canonly be optimized for a specific speed range. Especially in the area ofpartial load and idling, i.e. when small fuel-injection quantities andlow filling degrees and/or low speed are involved the required vortexformations can only be achieved by throttling. This, however, results inhigher fuel consumption. Moreover, it is disadvantageous that thewall-directed fuel-injection system requires a more costly piston designwith a deflection edge.

[0007] From German Patent No. 38 08 635, a fuel injection device for thedirect injection of fuel into the cylinder of a mixture-compressinginternal combustion engine is known in the form of an air-directedfuel-injection system. The fuel injection device includes a fuelinjector, which is positioned in the cylinder wall at a certain distancefrom the cylinder head and across from the discharge orifice; it has anoutlet opening, the jet axis of the fuel injector being directed to theregion around the spark plug positioned in the cylinder head. The fuelinjector includes a magnet-activated valve needle provided with helicalswirl grooves to generate a swirl flow of the injection jet. The entirecross-sectional area of the swirl grooves is smaller than thecross-sectional surface of the outlet opening by at least half, the fuelinjector being positioned above a flushing orifice and its jet axispointing to the ignition point located in the center of the cylinderhead. Owing to the air stream, the injected fuel is carried along in thedirection of the spark plug and conveyed thereto without touching thecylinder wall.

[0008] In air-directed fuel-injection systems as well, the mixtureconveyance to the spark plug is less than successful in idling operationand in lower partial-load operation, due to the aforementioned reasons;in mean partial-load operation it is partly only possible withunjustifiably low production variances of the high-pressure fuelinjectors utilized and/or the flow guidance through the intake manifold.The faulty reproducibility primarily manifests itself in increasedemissions of unburned hydrocarbons as a result of individual combustionmisses.

[0009] From German Published Patent Application No. 198 04 463, ajet-directed fuel injection system for mixture-compressing internalcombustion engines having external ignition is known, which includes atleast one fuel injector injecting the fuel into a combustion chamberhaving a piston/cylinder design, and which is provided with a spark plugprojecting into the combustion chamber. The nozzle body of the fuelinjector is located in the vicinity of the spark plug, which is in thecenter of the combustion chamber, and it is provided with at least onerow of injection orifices distributed over the circumference of thenozzle body. By selectively injecting fuel via the injection orifices, ajet-controlled combustion method is realized by a mixture cloud beingformed, at least one jet being aimed in the direction of the spark plug.Additional jets ensure that an at least approximately continuous orcohesive mixture cloud is formed.

[0010] A method of forming an ignitable fuel/air mixture is known fromGerman Patent No. 196 42 653. An ignitable fuel/air mixture can beformed in the cylinders of internal combustion engines having directinjection in that an injector injects fuel into each combustion chamberbounded by a piston upon release of a nozzle orifice in response to avalve member lifting off from a valve seat which encircles the nozzleorifice. To produce an internal mixture formation that is optimized withrespect to consumption and emissions, in every operating point of theentire characteristics map, under all operating conditions of theinternal combustion engine, particularly in stratified operation, theopening stroke of the valve member and the injection time are variablyadjustable.

[0011] Disadvantageous in jet-directed fuel-injection systems is thatcurrently used cylinder heads having a spark plug centrally positionedin the cylinder axis in the cylinder head, can only be used whensubstantially modified, since the additional installation space for thefuel injector in the vicinity of the spark plug requires adisadvantageous moving of the, in most cases, two intake valves.

[0012] While the currently used production tools and cylinder-headdesigns may in fact be compatible when the fuel injector is positionedin the cylinder wall on the side of the intake valves, theafore-described disadvantages of the air-directed and the wall-directedfuel-injection systems still occur.

SUMMARY OF THE INVENTION

[0013] In contrast, the fuel-injection system according to the presentinvention has the advantage over the related art that it allows the fuelinjector to be placed on the cylinder wall in the cylinder head, on theside of the intake valves. Moreover, in the manufacture, the cylinderhead is compatible with the currently used cylinder heads for manifoldinjection, and the disadvantages of the wall-directed and theair-directed fuel-injection systems are avoided, since thefuel-injection system according to the present invention is ajet-directed fuel-injection system. Contrary to preconceived notions ofthe technical world, it has been shown that a jet-directed mixture cloudis able to be generated in partial-load operation even from the positionof the fuel injector provided for in the fuel-injection system accordingto the present invention. A fuel jet of a multiple-orifice fuel injectormay be injected with sufficient precision through half the cylinderdiameter.

[0014] Moreover, it is advantageous that the mixture formation forignition does not rely on a vortex being formed, and thecombustion-chamber geometry, especially the piston design, may be freelyselected so that it is optimal in view of additional aspects.

[0015] In particular, thermal-shock load and coking of the spark plugare reduced by the tangential injection of fuel relative to thespark-plug position. The fuel jets, thus, are not directly aimed at thespark plug.

[0016] Furthermore, it is advantageous that, given an appropriatelyselected angle, a favorable ignition curve is able to be achieved by twoinjection jets and by placing the spark plug on the bisectrix betweenthese fuel jets.

[0017] Additional fuel jets may advantageously be directed towards theremaining combustion chamber that is formed when the piston isapproximately in the vicinity of top dead center.

[0018] In particular, it is possible to advantageously allocate the fueljets to three planes, which assume identical angles of betweenapproximately 20° and 30° with respect to each other. In this context,the uppermost plane, which is closest to the cylinder head, is made upof the two fuel jets flanking the spark plug; the second is made up ofthree fuel jets, of which the center jet is located on the bisectrix ofthe fuel jets of the first level, projected in the direction of thecylinder axis, and the lowest plane in turn is made up of two fuel jetspositioned beneath those of the first plane. Such a design of the fueljets allows good propagation of the flame front across the three planes,following ignition.

[0019] The piston may be designed to include a quenching edge and apiston recess, and the form of the jet pattern may be adjusted to thecombustion chamber determined thereby.

[0020] The fuel jets may be flat jets, which are injected through slitsas spray-discharge orifices.

[0021] In an alternative, advantageous specific embodiment, theadditional fuel jets are located in a plane together with the fuel jetsthat are in tangential alignment with respect to the spark plug; theyare even in number and positioned on both sides of the spark plug inmatching numbers.

[0022] This specific embodiment allows an advantageous mixtureformation, especially when no piston recess is provided, or only a veryshallow one.

BRIEF DESCRIPTION OF THE DRAWINGS

[0023]FIG. 1 shows a schematic section through a fuel-injection systemaccording to the related art for a wall-directed combustion method.

[0024]FIG. 2 shows a schematic section through a fuel-injection systemaccording to the related art for an air-directed combustion method.

[0025]FIG. 3 shows a schematic section through a fuel-injection systemaccording to the related art for a jet-directed combustion method.

[0026]FIG. 4 shows a schematic section through a first exemplaryembodiment of the fuel-injection system designed according to thepresent invention.

[0027]FIG. 5 shows a schematic representation of the spray-dischargesection of the fuel injector in FIG. 4, in a plan view, and itsorientation toward the spark plug.

[0028]FIG. 6 shows a schematic representation of the spray-dischargesection of the fuel injector of FIG. 4, in a side view.

[0029]FIG. 7 shows a schematic representation of the spray-dischargesection of the fuel injector of FIG. 4 in an advantageous specificembodiment, in a side view.

[0030]FIG. 8 shows a schematic representation of the spray-dischargesection of the fuel injector of FIG. 7, in a plan view.

DETAILED DESCRIPTION

[0031]FIGS. 1, 2 and 3 schematically show the basic design of the threemost important fuel-injection systems according to the related art, tofirst delineate the respective advantages and disadvantages and toexplain to what extent the present invention combines the advantages ofthe fuel-injection systems while avoiding the disadvantages.

[0032]FIG. 1 shows a schematic section through a fuel-injection systemaccording to the related art for a wall-directed combustion method. Apiston 2 is guided in a cylinder 1, represented schematically in acut-away view. A combustion chamber 3 is delimited by a cylinder head 4resting on cylinder 1. A spark plug 5 is in the center of cylinder 1,and a discharge valve 6 and an intake valve 7 are located on the side,for the gas exchange. Normally, two intake valves 7 and discharge valves6 are provided in most cases. A fuel injector 8 is located in cylinderhead 4 on the side of intake valve 7 toward the wall of cylinder 1.Piston 2 has a distinctly formed piston recess 9 and, approximately inthe piston center, a deflection edge 10 which delimits piston recess 9.

[0033] Fuel injector 8 injects fuel in the direction of piston recess 9.This is indicated in FIG. 1 by a fuel cloud 11. In the process, the fuelstrikes the vortex, formed by air, and piston recess 9. The vortexcauses the fuel to be carried to deflection edge 10 and, forming amixture, conveys it to spark plug 5. The path of this mixture cloud isindicated by an arrow.

[0034]FIG. 2 shows a schematic section through a fuel-injection systemaccording to the related art for an air-directed fuel-injection system.To the extent that the basic design is identical to the components ofcylinder 1, piston 2, combustion chamber 3, cylinder head 4, spark plug5, discharge valve 6, intake valve 7 and fuel injector 8 of FIG. 1, thesame reference numerals have been used. In a departure, a relativelyflat piston recess 12 is formed at piston 2.

[0035] Fuel injector 8 injects the fuel in the direction of a vortex incombustion chamber 3. This is indicated by a fuel cloud 13 in FIG. 2.Because of the vortex, the fuel, forming a mixture, is propelled tospark plug 5 without making contact with a wall. The path of thismixture cloud is indicated by an arrow.

[0036] Wall-directed and air-directed fuel-injection systems offer theadvantage of a convenient placement of fuel injector 8, which allowscylinder head 4 to be very similar to conventional cylinder heads forthe manifold injection and the continued use of production facilities.Disadvantageous is the always required vortex formation, whichcomplicates an optimization of the combustion chamber in view of otheraspects, and which can only be optimized for certain speeds and loadstates; it also leads to throttling losses.

[0037]FIG. 3 shows a schematic section through a fuel-injection systemaccording to the related art for a jet-directed combustion method. Tothe extent that the basic design is identical to the components ofcylinder 1, piston 2, combustion chamber 3, cylinder head 4, spark plug5, discharge valve 6, intake valve 7 and fuel injector 8 of FIG. 1, thesame reference numerals have been used. In a departure, a fuel injector14 and a spark plug 15 are centrally positioned in the center ofcylinder 1 in combustion chamber 3.

[0038] A mixture cloud 15, made up of individual fuel jets, is injectedinto combustion chamber 3 by fuel injector 14. In the process, at leastportions of fuel cloud 16 are injected directly toward the vicinity ofspark plug 14 where they produce an ignitable mixture. A jet-directedfuel-injection system offers the advantage of relative freedom in thedesign of the remaining combustion chamber 3. In addition, there are nothrottling losses. Disadvantageous is the placement of fuel injector 15,which is unfavorable from the viewpoint of production engineering andinstallation space.

[0039]FIG. 4 shows a schematic section through a first exemplaryembodiment of the fuel-injection system according to the presentinvention; it has a piston 16, which is guided in a cylinder bore 17 anddelimits a combustion chamber 19 together with a cylinder head 18. Aspark plug 20 is located in the center of cylinder bore 17, and adischarge valve 21, having outlet channel 22, and an intake valve 23,having an intake channel 24, are located on the side for the gasexchange. Normally, two intake valves 23 and discharge valves 21 areprovided in most cases. A fuel injector 25 is located in cylinder head18 on the side of intake valve 23 toward the wall of cylinder bore 17.Piston 16 has a distinctly formed piston recess 26 and a quenching edge27 delimiting piston recess 26.

[0040] Piston 16 is shown in cylinder bore 17 in a positioncorresponding to the instant when fuel is injected through fuel injector25. Fuel injector 25 has spray-discharge orifices, which are configuredsuch that fuel jets 28 of a first plane spray-discharge towards theregion of spark plug 20. With respect to the planes, fuel jets 29 of asecond plane assume an angle γ1 relative to the fuel jets of the firstplane. Fuel jets 30 of a third plane, which, with respect to the planes,assume an angle γ2 relative to the fuel jets of the second plane, fillthe region of piston recess 26. Arrows indicate the fuel jets. Angle γ1is identical to angle γ2.

[0041]FIG. 5 shows a schematic representation of a spray-dischargesection 31 of fuel injector 25 of FIG. 4, in a plan view, and itsorientation toward spark plug 20. Fuel jets 29, 30, 31, indicated byarrows, of the three planes are spray-discharged from spray-dischargeorifices 32. In the exemplary embodiment described here, two fuel jets29 of the first plane are aligned tangentially with respect to sparkplug 20 and oriented such that spark plug 20 is located on a bisectrixof fuel jets 29 of the first plane. A dotted line between the arrowheadsshows the configuration in one plane. Three fuel jets 30 of the secondplane are configured to be offset from fuel jets 29 of the first plane,so that the center fuel jet 29 a is oriented underneath spark plug 20.Two fuel jets 30 of the third plane are directed underneath fuel jets 28of the first plane.

[0042]FIG. 6 shows a schematic representation of spray-discharge section31 of fuel injector 25 of FIG. 4 in a side view, viewed from thedirection of spark plug 20. Spray-discharge orifices 32 are distributedover a spherical surface 33 in three rows. This configuration makes itpossible to achieve a spray-discharge in three planes.

[0043] In the specific embodiment of the present fuel-injection systemaccording to the present invention, fuel injector 25 is advantageouslyable to be positioned on the side of combustion chamber 19, therebymaking it highly compatible with conventional cylinder heads. Theremaining combustion chamber may be designed relatively freely, sincefuel jets 29 of the first plane form an ignitable mixture in the regionof spark plug 20. In particular, due to the present advantageousspecific embodiment, the entire combustion chamber 19, including theregion of piston recess 26, is able to be reached by fuel jets. Contraryto the currently held view, it has been shown that it is possible toinject a fuel jet 28 from the side of combustion chamber 19 toward sparkplug 20.

[0044]FIG. 7 shows a schematic representation of spray-discharge section31 of fuel injector 25 of FIG. 4 in an alternative, advantageousspecific embodiment, in a side view, viewed from the direction of sparkplug 20. Instead of spray-discharge orifices, slits 34 are provided inthis case, thereby making it possible to produce flat jets. A web 35prevents fuel from being spray-discharged directly onto spark plug 25.

[0045]FIG. 8 shows a schematic representation of spray-discharge section31 of fuel injector 25 of FIG. 7 in a plan view. Slits 34 and web 35 areshown.

[0046] The present invention is not limited to the exemplary embodimentsshown, and is also applicable, for instance, to fuel-injection systemshaving more or fewer injection orifices, intake and discharge valves,and, in particular, more spark plugs and variable cubic capacity.

What is claimed is:
 1. A fuel injection system for internal combustionengines having at least one fuel injector (25) injecting fuel into acombustion chamber (19), which is delimited by a cylinder wall (17) inwhich a piston (16) is guided, and having a spark plug (20) projectinginto the combustion chamber (19), the fuel injector (25) being locatedin the combustion chamber (19) in the region of a gas-intake valve (23)toward the cylinder wall (17) and producing a plurality of fuel jets(28, 29, 30), wherein at least one fuel jet (29) has a tangentialorientation into the region of the spark plug (20).
 2. Thefuel-injection system as recited in claim 1, wherein spray-dischargeorifices (32) of the fuel injector (25) are distributed in such a mannerthat at least two fuel jets (28) are injected at a predefined openingangle into the combustion chamber (19), tangentially to the spark plug.3. The fuel-injection system as recited in claim 2, wherein the sparkplug (20) is located on the bisectrix of the opening angle.
 4. Thefuel-injection system as recited in claim 3, wherein the opening angle,as a function of a clearance of the fuel injector (25) to the spark plug(20), is dimensioned such that an ignitable mixture is produced on bothsides tangentially to an ignition electrode of the spark plug (20). 5.The fuel-injection system as recited in claim 4, wherein, at a pistonposition essentially near top dead center, additional fuel jets (29, 30)are evenly aligned with the remaining combustion chamber (19).
 6. Thefuel-injection system as recited in claim 5, wherein the fuel jets (28,29, 30) are oriented in three planes at an angle γ1 between the firstand second plane, and at an angle γ2 between the second and third plane,the first plane, which is closest to the cylinder head (18), beingformed by the two fuel jets (18) that are tangentially aligned to thespark plug (20).
 7. The fuel-injection system as recited in claim 6,wherein the second plane is formed by three fuel jets (30) which areoffset with respect to the fuel jets (28) of the first plane, and thecenter fuel jet (29 a) is beneath the bisectrix of the opening angle ofthe fuel jets (29) of the first plane.
 8. The fuel-injection system asrecited in claim 7, wherein the third plane is made up of two fuel jets(30) which are located beneath the fuel jets (28) of the first plane. 9.The fuel injection system as recited in one of claims 6 through 8,wherein the angle γ1 has a value of between 20° and 30°.
 10. The fuelinjection system as recited in one of claims 6 through 9, wherein theangle γ2 has a value of between 20° and 30°.
 11. The fuel injectionsystem as recited in one of claims 6 through 9, wherein the angle γ1 isidentical to angle γ2.
 12. The fuel-injection system as recited in claim5, wherein the fuel jets are oriented in one plane.
 13. Thefuel-injection system as recited in claim 12, wherein there is an evennumber of fuel jets, and a matching number is aligned on both sides ofthe spark plug (20).
 14. The fuel injection system as recited in one ofclaims 1 through 13, wherein the fuel jets are flat jets and are formedby longitudinal spray-discharge orifices of the fuel injector (25). 15.The fuel-injection system as recited in claim 14, wherein thespray-discharge orifices are slits (34).
 16. The fuel-injection systemas recited in claim 15, wherein the slits are subdivided by webs (35).17. The fuel injection system as recited in one of claims 1 through 16,wherein the piston (16), on the side lying opposite from the fuelinjector (25) relative to a cylinder center axis, is provided with aquenching edge (27).
 18. The fuel injection system as recited in one ofclaims 1 through 17, wherein the piston (16) has a piston recess (26).19. The fuel-injection system as recited in claim 18, wherein the pistonrecess (26) is adapted in its form to the form of the jet pattern of thefuel injector (25), and no fuel jet (28, 29, 30) directly strikes thepiston surface.